1. Field of the Invention
This invention relates to ignition devices for use in a high mechanical shock environment, such as the ignition of liquid propellant in a gun, or the ignition of fuel in a jet engine.
2. Prior Art
The use of an igniter, per se, in a liquid propellant gun is shown by Broussard in U.S. Pat. Nos. 2,088,503, issued July 27, l937; Rost in 2,129,875, issued Sept. 13, 1938; Barbieri et al. in 3,326,084, issued June 20, l967; Myers in 3,673,917, issued July 4, 1972; Nelson et al. in 3,728,937, issued Apr. 24, 1973; Tassie in 3,763,739, issued Oct. 9, 1973; and Broxholm et al., 3,949,642 issued Apr. 13, 1976. Of these, Tassie and Broxholm et al. show the igniter coaxially mounted in the gun bolt, as does Mitchell in U.S. Pat. No. 3,608,492, issued Sept. 28, 1971 in a gun firing caseless ammunition.
The conventional igniter is an assembly of solid, rigid parts. The main insulator is usually a hard, high-fire ceramic, which is then combined with seals and fitted inside a strong, outer case which also serves as the outer conductor or electrode. The center electrode together with seals is fitted through a longitudinal bore in the main insulator. In a high mechanical shock environment, i.e., high pressure pounding, the assembly deteriorates: the seals deteriorate; the ceramic cracks, or one part slips with respect to another. Such slippage causes more breakage; the seal fails, combustion gas leaks, and eventually the igniter even fails to spark.
Accordingly, it is an object of this invention to provide an igniter which is unaffected by a high mechanical shock environment.
An additional object of this invention is to provide a gun bolt and igniter assembly which is effective in a liquid propellant gun.
Another object of this invention is to provide a process for the manufacture of such an igniter.
A feature of this invention is the provision of an igniter assembly comprising an outer tubular conductor and an inner conductor spaced apart by a volume of tightly packed, irregular granules of an insulating material, such as a mineral powder. The outer conductor is supported in a longitudinal bore of a gun bolt.